One of the first details everyone heard about the HTC Nexus One, aka the “Google Phone” is just how lusciously thin it is.

That’s important in a smartphone. The trend in phones towards minimization has increasingly shifted away from making phones smaller on the x and y axis, which decreases the phone’s functionality, and shrinking its z axis, which makes a phone feel smaller and lighter without negatively impacting its ease of use.

So how thin is the Nexus One? At first, all we heard was that it was thinner than Apple’s iPhone, which is no mean trick, but now, thanks to an intrepid Google mole, we’ve got an even better idea of the Nexus One’s svelteness.

According to an image published by Boy Genius Report comparing the Nexus One lying side by side with the first Android phone, the T-Mobile G1, the Google Phone is only half the thickness of the latter phone. Since the G1 is around 17mm thick, it makes sense to estimate the Google Phone to be around 10mm.

Now, granted, the G1 was never described as svelte… but 10mm is still a significant decrease in depth from the iPhone. Thinness matters in smartphone design: it’s the new sexy. For a company as obsessed with thinness as Apple, this has to have their design departments scrambling to shrink down the iPod’s already tightly packed chassis.